Sea trials are fairly standardized using technical bulletins published by ITTC, SNAME, BMT, regulatory agencies or the owners. They involve demonstrations and tests of the ship’s systems and performance.
- Speed trial: Ballasted or Loaded to a predetermined draft. Propulsion machinery set to the contracted maximum service setting. Usually some percentage of the machinery’s maximum continuous rating. (ex: 90% MCR). Ship’s heading adjusted to have the wind and tide as close to bow-on as possible. Allowed to come to speed and the speed is continuously recorded using differential GPS. Ship is then turned through 180° with the procedure being repeated which reduces the impact of wind and tide. The final “Trials Speed” is determined by averaging all of the measured speeds during each of the runs. This process may be repeated in various sea states.
- Crash stop: Ballasted or loaded to a predetermined draft. Propulsion machinery set to the contracted maximum service setting. Starts at once receiving the order to “Execute Crash Stop”. At this point, propulsion machinery set to full-astern and the helm is put hard-over to either port or starboard. The speed, position and heading are continuously recorded using differential GPS. Final time to stop (i.e.: ship speed is 0 knots) track line, drift (distance traveled perpendicular to the original course) and advance (distance traveled along the original course line) are all calculated. The trial may be repeated at various starting speeds.
- Endurance: Ballasted or loaded to a predetermined draft. Propulsion machinery set to the contracted maximum service setting. The fuel flow, exhaust and cooling water temperatures and ship’s speed are all recorded.
- Maneuvering trials:A number of trials conducted to determine the maneuverability and directional stability of the ship. Include a direct and reverse spiral manoeuvres, Zig-Zag, and lateral thruster use.
- Seakeeping:Was used exclusively for passenger ships but now used in a variety of vessels. Involves measurements of ship motions in various sea states followed by a series of analyses to determine comfort levels, likelihood of sea sickness and hull damage. Trials are usually protracted in nature due to the unpredictability of finding the correct sea state and the need to conduct the trials at various headings and speeds.
Oh, By the Way, I just found some interesting facts relating to sea trials on Wikipedia. Here they are.
- RMS Lusitania – While steaming at high speeds, severe vibration was noted at the stern during her sea trials. This prompted her builder, John Brown & Company, to reinforce that area before acceptance by Cunard.
- SS Normandie – During sea trials, vibration was noted at the ship’s stern. The stern was reinforced, accepted by her owners Compagnie Générale Transatlantique, and continued onto her maiden voyage. The vibration was severe enough to necessitate relocating Tourist Class passengers and some crew members with cabins near the affected area. The problem was subsequently resolved by changing her propellers to four-bladed ones from the original three-bladed ones.
- RMS Queen Mary 2 – Her trials were conducted over two periods, September 25–29, 2003 and November 7–11, 2003, each lasting four days at sea, shuttling between the islands of Belle-Ile and L’ile d’Yeu off the French coast. On board for each set of trials were 450 people, including engineers, technicians, owner and insurance company representatives, and crew.
- USS Thresher (SSN-593) – Lost during deep sea diving tests on April 10, 1963.
The last one is the most amazing disaster that could happen in a trial. Such a misfortune. It sank with all hands during deep diving tests, 10 April 1963, 129 died. Such a tragic accident. It was a watershed event for the U.S. Navy, leading to the implementation of a rigorous submarine safety program known as SUBSAFE. Measured by lives lost, historic context and significance, the sinking of Thresher was then, and remains today, the world’s worst submarine disaster. As the first nuclear submarine lost at sea, its disappearance generated international shock and sympathy.
Htike Aung Kyaw
References:
– Ship Production, Second Edition, by Richard Lee Storch, Colin P. Hammon, Howard M. Bunch and Richard C. Moore
– The GlobMaritime Network
– Sea Trial – Wikipedia
